1. Field of the Invention
The present invention relates to an external type regulator for a vehicle alternator, and in particular to an external type regulator for a vehicle alternator which is capable of preventing a damage of electric parts and a battery by stopping a power generation by disconnecting a field current flowing in a field coil through a relay in the case that an over charge occurs in an alternator due to a damage of a regulator.
2. Description of the Background Art
Generally, a vehicle includes various electric apparatuses such as lamps, air conditioner, etc. including an electric part such as a starting apparatus or ignition apparatus of an engine. A battery and alternator supply a power to the above parts.
Namely, the alternator is connected with an engine by a certain belt. The generated power is determined based on the revolution of the engine. In the case that the generated power of the alternator is smaller than the load of various electric parts, namely, the load generated by load elements, the battery temporarily charges as a power source, so that the power charged in the battery is supplied to various load elements. In the case that the generated power of the alternator is larger than the load generated in various load elements, only the alternator supplies the power to all load elements, and the battery is charged by the alternator.
At this time, a regulator is used together with the alternator for supplying a power proper to various loads and charging a battery by a certain amount by controlling the output voltage of the alternator by controlling the field current flowing in the field coil of the alternator.
FIG. 1 is a view illustrating a regulator for a conventional vehicle alternator. The above regulator includes a charge lamp controller 10 for controlling in order for a charge lamp to be turned on when a vehicle is in a key-switch on state and in order for the charge lamp to be turned off when the engine starts, and the alternator generates the power, and a voltage adjusting unit 20 for controlling in order for the output voltage of the alternator to be constantly maintained as an adjusted voltage.
In the case of the charge controller 10, when the key switch of the vehicle is turned on, the current of the battery (not shown) is inputted into a terminal L connected with the charge lamp (not shown) through an ignition key (not shown). When the current flowing from the terminal A connected with an output voltage terminal of the alternator (not shown) through a resistor R1 is inputted into a base terminal of a transistor Q7, the transistor Q7 is turned on, and a transistor Q8 is turned on, so that the current of the battery inputted into the terminal L flows to the earth terminal E through the transistor Q8, whereby the charge lamp is turned on.
In addition, when the alternator generates power as the engine starts, the current flowing from the terminal A through the resistor R1 is inputted into a collector terminal of a transistor Q6. When the current flowing from a terminal N connected with the center point of the alternator through a diode D3 and the resistor R2 is inputted into a base terminal of the transistor Q6, the transistor Q6 is turned on, and the transistors Q7 and Q8 are turned off, so that the current of the battery does not flow to the charge lamp connected with the terminal L. Namely, the current directly flows to the terminal E for thereby turning off the charge lamp.
In the case of the voltage adjusting unit 20, the current of the battery is inputted into the IG terminal connected with the ignition key and is inputted into the collector terminal of the transistor Q2 through the diode D7 and a resistor R9. When the current flowing from the terminal F connected with the field coil (not shown) through a condenser C2, a resistor R11 and a condenser C1 is inputted into a base terminal of the transistor Q2, the transistor Q2 is turned on, and the current flowing in an emitter terminal is inputted into a base terminal of the power transistor Q4 directly connected with the terminal A.
Therefore, the power transistor Q4 is turned on, and the current of an emitter terminal flows to the field coil through the terminal F for thereby first exciting the field coil.
The output voltage of the alternator becomes constant as described in the following operation.
When the output voltage of the alternator is higher than the adjusting voltage, the transistor Q1 directly connected with the terminal A is turned on. Therefore, the current directly flows to the terminal E through a resistor R8. As the transistor Q1 is turned on, when the output voltage of a resistor R11 is higher than the conducting voltage of a zenor diode D5, the zenor diode D5 is turned on, and the current flows to the terminal E through the transistor Q1, the resistor R11, the zenor diode D5, the diode D6 and the resistors R13, R14 and R15.
Therefore, the current is not inputted into a base terminal of the transistor Q2, and the power transistor Q4 is turned off. So, the current does not flow to the field coil connected with the terminal F, so that it is impossible to generate power, whereby the generating voltage is decreased.
Next, when the output voltage of the alternator becomes lower than the adjusting voltage, namely, as the output voltage of the alternator at the resistor R11 is lower than the conducting voltage of the zenor diode D5, when the zenor diode D5 is turned off, and the transistor Q1 is turned off, the current flowing from the terminal N to the diode D4 and the resistor R4 is inputted into a base terminal of the transistor Q5. When the transistors Q3 and A2 are turned on by the current flowing in the terminal A, the power transistor Q4 is turned on, and the current flowing in the terminal A flows to the terminal E through the field coil connected with the terminal F through the power transistor Q4, so that the generating voltage is increased.
In the conventional art, the above described operation is repeatedly performed at a very high speed for thereby maintaining the voltage generation of the alternator as a uniform adjusting voltage.
In the conventional art, the heat sink which is a kind of heat radiating plate is used for preventing an over heating phenomenon of the power transistor Q4 in the voltage adjusting unit 20.
Namely, if the power transistor Q4 becomes a short circuit state due to the over heating of the power transistor Q4, the regulator does not normally perform the regulation function.
In the conventional art, the over heating problem of the power transistor Q4 is prevented using the heat sink in the above described manner. However, since the heat sink is simply fixed using screws at a certain portion of a substrate on which the power transistor Q4 is mounted, if the screws are not properly fixed, a non-contact problem may occur, so that the heat sink may not normally operate.
Namely, when the heat sink function is not properly performed, the over heating problem of the power transistor Q4 may occur, so that the power transistor Q4 may be critically damaged. Furthermore, the regulator may be damaged, so that the over change problem may occur in the alternator. Therefore, the electric parts of the vehicle may be critically damaged due to the over charge of the alternator. In addition, the battery may be damaged for thereby decreasing the life span of the battery.
Accordingly, it is an object of the present invention to provide an external type regulator for a vehicle alternator which overcomes the problems encountered in the conventional art.
It is another object of the present invention to provide an external type regulator for a vehicle alternator which is capable of preventing any damage of electric parts and battery of a vehicle by detecting an over charge of an alternator through a zenor diode in the case that an over charge occurs in an alternator due to a damage of a regulator and stopping a power generation of an alternator by disconnecting a field current flowing between a power transistor and a field coil through a relay driven by two transistors.
In order to achieve the above objects, there is provided an external type regulator for a vehicle alternator which includes an over charge disconnector which includes a dividing resistor for dividing a voltage inputted through an IG terminal, a zenor diode which is turned off in the case that the voltage divided by the dividing resistor is higher than a zenor voltage, for thereby detecting an over charge of an alternator which occurs in an IG terminal, first and second transistors which are turned on when the zenor diode detects an over charge and is turned on and outputs a relay driving signal, a relay which has a contact point terminal connected between a power transistor and a field coil of the voltage adjusting unit and being switch-driven in response to a relay driving signal when the first transistor is turned on, for thereby disconnecting a field current flowing between the power transistor and the field coil, and a plurality of resistors, condensers and diodes, whereby the over charge disconnector stops a power generation of the alternator by detecting an over charge of the alternator and disconnecting a field current flowing in the field coil.